This invention relates generally to a system for electrodeposition of paint, or other coatings, on articles of manufacture; and more practicably to a workholder for retaining and carrying said articles during the electrodeposition process.
In one type of paint electrodeposition system items to be painted are submerged in each of a succession of tanks or vats containing, for example, cleaning solutions or solvents, surface preparation solutions, and/or paints. As is well known, an electrodeposition system by its very nature requires that while the items proceed through each of the tanks, they must be maintained on a carrier in such fashion that an electrical path is established through the contents of the tank, through the items, through the workholder, and eventually back to the tank contents via an electromotive source. It can be readily understood that it is desirable to maintain good electrically-conductive contact between the items to be painted and the workholder.
Further it is desirable to provide a workholder which permits quick and efficient racking and unracking of the items to be painted from the workholder. Also important is the racking density achievable on the carrier system employed, which should be as dense as practically possible without interfering with the painting or racking and unracking of the items.
Typically the items to be painted are carried on magnetic retainers, or placed on simple open-ended hooks secured, for example, to a carrier with set screws. Disadvantages with the prior art include the less than adequate electrical contact provided under certain adverse conditions, for example, when paint previously deposited upon the retainer or the hook inhibits electrical conduction across the contact area to the item. This at times requires an operator to clean the retainer or hook manually. Further, another disadvantage with magnetic retainers, is that the paint may reduce the magnetic retention resulting in items being dislodged from the retainer during electrodeposition. A disadvantage, when a simple hook is used in conjunction with light items to be painted, is that the items tend to float in the various tanks and therefore the items may be dislodged from the hooks or make inadequate electrical connection with the carrier. A still further disadvantage with the prior art is the degree of scarring produced by such carriers. A scar is any area left unpainted on the workpiece after paint electrodeposition and may be most undesirable for at least aesthetic reasons. Thus the prior art suffers many potential disadvantages.
Therefore, an object of the invention is to provide workholders and carrier for items to be painted in an electrodeposition system which maintain the items securely thereon and provide good electrical contact between the item, the holder and the carrier.
Another object of the invention is to provide a workholder and carrier for such a paint system which minimizes or reduces scarring on the item due to the carrier.
A further object of the invention is to provide a workholder and carrier for such a paint system which enables facilitated racking and unracking of items to be painted from said workholder and further enables high density carrying of items to be painted.
Yet another object of the invention is to provide a versatile, economical workholding system which can accommodate a variety of sizes, shapes and weights of items to be painted.